U.S. patent application number 13/536212 was filed with the patent office on 2013-01-03 for drilling/reaming tool.
This patent application is currently assigned to KENNAMETAL, INC.. Invention is credited to HERBERT RUDOLF KAUPER, JURGEN SCHWAEGERL.
Application Number | 20130004253 13/536212 |
Document ID | / |
Family ID | 47355189 |
Filed Date | 2013-01-03 |
United States Patent
Application |
20130004253 |
Kind Code |
A1 |
KAUPER; HERBERT RUDOLF ; et
al. |
January 3, 2013 |
DRILLING/REAMING TOOL
Abstract
A drilling/reaming tool includes a basic body which extends in a
longitudinal direction. The basic body includes at least one
end-side drilling major cutting edge, a main flute which is
assigned to said drilling major cutting edge and is wound at a
first helix angle, and a plurality of reaming cutting edges which
are arranged circumferentially on the basic body and have in each
case one reamer flute which is assigned to the respective reaming
cutting edge and is wound at a second helix angle. The reaming
cutting edges adjoin the at least one major cutting edge directly
in the longitudinal direction. Each reamer flute is merged into the
main flute.
Inventors: |
KAUPER; HERBERT RUDOLF;
(ERLANGEN, DE) ; SCHWAEGERL; JURGEN;
(VOHENSTRAUSS, DE) |
Assignee: |
KENNAMETAL, INC.
Latrobe
PA
|
Family ID: |
47355189 |
Appl. No.: |
13/536212 |
Filed: |
June 28, 2012 |
Current U.S.
Class: |
408/59 ;
408/230 |
Current CPC
Class: |
Y10T 408/455 20150115;
Y10T 408/906 20150115; B23D 2277/52 20130101; Y10T 408/9097
20150115; B23B 51/08 20130101; B23B 2251/046 20130101; B23D 77/00
20130101 |
Class at
Publication: |
408/59 ;
408/230 |
International
Class: |
B23B 51/08 20060101
B23B051/08; B23D 77/00 20060101 B23D077/00; B23B 51/06 20060101
B23B051/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 2, 2011 |
DE |
102011106416.1 |
Claims
1. A drilling/reaming tool comprising: a basic body which extends
in a longitudinal direction and includes: at least one end-side
drilling major cutting edge; a main flute which is assigned to said
drilling major cutting edge and is wound at a first helix angle;
and a plurality of reaming cutting edges which are arranged
circumferentially on the basic body and have in each case one
reamer flute which is assigned to the respective reaming cutting
edge and is wound at a second helix angle, wherein the reaming
cutting edges adjoin the at least one major cutting edge directly
in the longitudinal direction, and wherein each reamer flute is
merged into the main flute.
2. The drilling/reaming tool of claim 1 wherein the first helix
angle is different than the second helix angle.
3. The drilling/reaming tool of claim 1 wherein the second helix
angle is smaller than the first helix angle, and each reamer flute
opens into the main flute.
4. The drilling/reaming tool of claim 1 wherein the first helix
angle lies in the range of from about 15.degree. to about
40.degree. and the second helix angle lies in the range of from
about 0.degree. to about 20.degree..
5. The drilling/reaming tool of claim 1 wherein the first helix
angle is approximately 30.degree. and the second helix angle is
approximately 10.degree..
6. The drilling/reaming tool of claim 1 wherein the basic body has
a nominal diameter and wherein the reamer flutes are merged into
the main flute at an axial length in the range from 0.1 times to 4
times the nominal diameter.
7. The drilling/reaming tool of claim 1 wherein a reamer head is
configured which carries the major cutting edge and the reaming
cutting edges and which is adjoined in the longitudinal direction
by a part of the basic body, the part having a reduced diameter in
comparison with the reamer head, wherein the reamer head includes a
shoulder formed by the difference in diameter, and wherein the
reamer flutes open into the shoulder.
8. The drilling/reaming tool of claim 1 wherein the reamer flutes
are wound in the opposite direction to the main flute.
9. The drilling/reaming tool of claim 1 wherein the reaming cutting
edges have an unequal pitch.
10. The drilling/reaming tool of claim 1 wherein the reaming
cutting edge of the plurality of reaming cutting edge which adjoins
the main flute in the circumferential direction is recessed in the
longitudinal direction in relation to the following reaming cutting
edge of the plurality of reaming cutting edges.
11. The drilling/reaming tool of claim 1 wherein the plurality of
reaming cutting edges are arranged in such a way that each of the
reaming cutting edges has an identical cutting performance during
operation for a defined feed.
12. The drilling/reaming tool of claim 1 wherein coolant channels
which exit at end-side first openings are formed in the basic
body.
13. The drilling/reaming tool of claim 12 wherein
circumferential-side second openings which are connected to the
coolant channels are formed in the basic body, the second openings
being structured to provide a coolant in the reamer flutes.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The invention relates generally to rotary cutting tools used
to perform drilling/reaming operations.
[0003] 2. Background Information
[0004] An example of a tool upon which the present invention
improves is shown, for example, in DE 101 44 241 B4. The
drilling/reaming tool which is described in said document has two
(drilling) major cutting edges which are in each case assigned a
helical main flute which is machined into a basic body of the tool.
In addition, three reaming cutting edges which are spaced apart
from one another in the circumferential direction are provided on
the circumferential side, which reaming cutting edges project
somewhat beyond the major cutting edges in the radial direction.
Here, the reaming cutting edges adjoin the major cutting edges
directly. Each reaming cutting edge is assigned a reamer flute
which is likewise formed in a helically extending manner in a land
of the basic body between the two main flutes.
[0005] Drilling/reaming tools of this type serve for the production
of a drilled hole and for the simultaneous finishing operation of
the hole wall with the aid of the reaming cutting edges. The key
here is machining which is as highly precise as possible, in order
to achieve the desired surface quality of the hole wall. Here,
inter alia, effective transporting away of chips is also decisive.
It is to be avoided here, in particular, that a chip is jammed
between the wall of the hole and the tool, which would lead to
damage of the wall of the machined hole. Here, transporting away of
chips becomes more difficult as the depth of the drilled hole
increases.
[0006] There is thus room for improvements in rotary cutting tools
used to perform drilling/reaming operations.
SUMMARY OF THE INVENTION
[0007] The present invention improves upon the prior art by
providing an improved drilling/reaming tool that, among other
things, provides improved transportation of chips produced during
cutting operations.
[0008] According to an aspect of the invention, a rotary cutting
tool is provided. The rotary cutting tool comprises a basic body
which extends in the longitudinal direction and at least one,
preferably two or more drilling major cutting edges on its end
side, which drilling major cutting edges are in each case assigned
a main flute which is wound at a first helix angle. Reaming cutting
edges which are arranged on the circumferential side are provided
directly in the region of the end side, that is to say the drill
tip, which reaming cutting edges protrude radially beyond the major
cutting edges and therefore carry out a finishing operation on a
wall of a drilled hole which is formed by the major cutting edges.
Here, each reaming cutting edge is assigned a reamer flute. For
effectively transporting away the removed chips, in particular the
reaming chips which are removed by the reaming cutting edges, it is
provided that the reamer flutes are merged into the main flutes,
that is to say the reamer flutes are connected to the main flutes.
For transporting away the chips, it is therefore not required that
the reamer flutes, unlike the main flutes, are formed over the
entire length of a cutting part of the tool. In comparison with the
main flutes, the reamer flutes therefore extend only over a limited
axial length.
[0009] As a result of such arrangement, the comparatively small
reaming chips have to be guided in the reamer flutes only over a
small axial length. In particular in the case of relatively deep
drilled holes, the reaming chips are then guided away in the
usually considerably larger main flute, as a result of which the
risk of chips backing up and therefore also jamming of the reaming
chips between the hole wall and the tool is avoided. During
operation, the reaming chips are therefore preferably transported
away first of all in the reamer flutes approximately in the axial
direction and are subsequently guided into the main flute, where
they are then transported further away together with the drilling
chips which are formed by the major cutting edges.
[0010] It is of particular significance that the reaming cutting
edges adjoin the major cutting edges directly in the axial
direction. Here, directly is understood as meaning that no spacing
or at any rate a small axial spacing lies between the axially
rearmost part of the major cutting edge (cutting corner) and the
axially frontmost reaming cutting edge. In an example embodiment
the axial spacing is at most 1.0 times the nominal diameter of the
tool, in particular at most 0.1 times the nominal diameter.
[0011] Here, the reaming cutting edges extend radially to the
outside and are oriented, in particular, to the outside
perpendicularly with respect to the longitudinal axis. The
individual reaming cutting edges usually end on the same radial
circumference, and therefore have the same radius. This defines the
tool nominal diameter.
[0012] For effective transporting away of chips, the main flute and
the reamer flutes preferably have the same helix orientation. The
flutes are therefore preferably not configured in opposite
directions to one another, since, in this case and in the case of
drilling into solid material, if the reaming chips are combined
with the main chips, the risk of chips backing up would exist on
account of the different directions of flow.
[0013] According to an example embodiment of the invention, the two
helix angles are different from one another. Here, in particular,
the second helix angle of the reamer flute is smaller than the
first helix angle, with the result therefore that the reamer flutes
successively approach the main flute which is assigned to them in
each case and ultimately open into the main flute.
[0014] Here, the first helix angle of the main flute preferably
lies in the range from 15.degree. to 40.degree. and typically at
approximately 30.degree., and the second helix angle lies in the
range from 0.degree. to 20.degree., preferably at approximately
10.degree..
[0015] In an example embodiment, the reamer flutes are limited only
to a front region of the tool, that is to say they extend only over
a short axial length. The axial length preferably lies in the range
from one to four times the tool nominal diameter.
[0016] The tool can both be configured as a single-piece shank
tool, in which the major cutting edges, the drill tip, the reaming
cutting edges and the reamer flutes are machined in a single-piece
basic body. As an alternative, the tool can also be of modular
construction, in which a drilling/reamer head is inserted into a
basic body. Here, the reamer head can be inserted exchangeably or
else can be brazed in.
[0017] In an example embodiment of a modular tool in accordance
with the present invention, a reamer head is configured which
carries the major cutting edges and the reaming cutting edges and
the reamer flutes, and which is adjoined in the longitudinal
direction by a rearward part of the tool basic body which has a
reduced diameter in comparison with the reamer head, with the
formation of a shoulder. The reamer head and the rearward part
therefore merge into one another via a recessed shoulder. In this
design variant, it is provided that the reamer flutes open into
said shoulder and end there. It is not necessarily required here
that the reamer flutes meet the main flute and intersect with it.
In this design variant, the reaming chips can pass into an annular
space which is formed during operation between the hole wall and
the rearward radially recessed part of the basic body in the
circumferential direction to the main flute and are then guided
away in the latter. In this case, the annular space therefore forms
a connecting flute space between the reamer flutes and the main
flutes.
[0018] It is provided, in particular, in this design variant that
the helix angle of the reamer flutes is also greater than that of
the flute.
[0019] In an example embodiment, the main flutes and the reamer
flutes are wound in the same direction, that is to say they both
have, for example, a positive helix angle. As a result, the chips
are transported away in the two flute types in the same direction
and the reaming chips are guided into the main flute.
[0020] In an example embodiment, the main flutes and the reamer
flutes are wound in opposite directions, that is to say the main
flutes have, for example, a positive helix angle (greater than or
equal to 0.degree.) and the reamer flutes have a negative helix
angle (less than 0.degree.), preferably in the range down to
-40.degree.. As a result, the chips in the two flute types are
transported away in different axial directions. This refinement is
advantageous, in particular, for workpieces which are provided with
through holes. As a result of a negative helix angle of the reamer
flutes, the reaming chips are transported away to the front, that
is to say in the drilling direction.
[0021] In order to ensure as satisfactory a surface quality of the
wall of the hole as possible, high run-out and the avoidance of
what is known as a "juddering movement" are required. To this end,
an unequal pitch, in particular of the reaming cutting edges, is
preferably provided in general, in order to avoid resonance-like
building up of vibrations during the drilling operation. In order
to form the unequal pitch, different numbers of reaming cutting
edges are formed on the respective lands between the main flutes.
Typically, for example, at least two or three reaming cutting edges
are formed on the first land and three or four reaming cutting
edges are formed on the second land. The numbers of reaming cutting
edges preferably differ only by one reaming cutting edge.
[0022] As an alternative or in addition to this, it is provided
that the lands sweep over a different angular portion, that is to
say they have a different circumferential line. This is equivalent
to an unequal pitch of the major cutting edges; the latter
therefore have different angular spacings from one another. In the
case of two major cutting edges, this difference is, for example,
from 5.degree. to 10.degree.. In the case of two cutting edges, the
angular spacing is therefore (in the case of uniform distribution),
instead of the usual 180.degree., from 185.degree. to 190.degree.
on one side and from 170.degree. to 175.degree. on the other
side.
[0023] In principle, any combinations of unequal and equal pitch of
the number and distribution of the reaming cutting edges are
possible.
[0024] In an example embodiment, the first reaming cutting edge
which adjoins the major cutting edge in the circumferential
direction is recessed axially with regard to the further reaming
cutting edges. In general, it is provided in one expedient
refinement that the reaming cutting edges are configured and
arranged in such a way that they have an at least similar cutting
performance and are therefore loaded equally during operation in
the case of a predefined feed during cutting machining.
[0025] Since the first reaming cutting edge is assigned in a
leading manner the main flute, the first reaming cutting edge would
have to have a comparatively high cutting performance, if it were
situated at the same axial height as the further reaming cutting
edges. Here, the axial offset between the first reaming cutting
edge and the following second reaming cutting edge preferably
corresponds at least approximately to a proportionate axial feed
which the drilling tool covers in the case of correct use with a
defined feed over the rotary angle, over which the main flute
sweeps. The axial offset between the first and the second reaming
cutting edges typically lies in the range from 0.005 to 2 mm (in
the case of drilling nominal diameters in the range from 3 to 70
mm).
[0026] Coolant channels which open at first openings on the end
side are preferably formed in the tool basic body. In addition,
circumferential-side second openings are provided in the respective
reamer flutes close to the reaming cutting edges, in addition to
the end-side first openings, with the result that, in addition,
coolant is also provided directly at the reaming cutting edges in
an effective way. Here, the second openings in the reamer flutes
are preferably connected to the (main) coolant channels via
channels, in particular in the manner of branch channels or branch
bores. Here, the direct arrangement of the reaming cutting edges on
the end side and of both the first and second outlet openings
achieves cooling of the entire reamer head in an overall very
effective and efficient manner, that is to say of the frontmost
region of the tool, in which the reamer flutes are formed.
[0027] These and other objects, features, and characteristics of
the present invention, as well as the methods of operation and
functions of the related elements of structure and the combination
of parts and economies of manufacture, will become more apparent
upon consideration of the following description and the appended
claims with reference to the accompanying drawings, all of which
form a part of this specification, wherein like reference numerals
designate corresponding parts in the various figures. It is to be
expressly understood, however, that the drawings are for the
purpose of illustration and description only and are not intended
as a definition of the limits of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] A full understanding of the invention can be gained from the
following description of the preferred embodiments when read in
conjunction with the partially schematic figures in which:
[0029] FIG. 1 shows a side view of details of a drilling/reaming
tool,
[0030] FIG. 2 shows a perspective illustration of details of a
drilling/reaming tool,
[0031] FIG. 3 shows an end view of a drilling/reaming tool,
[0032] FIG. 4 shows a side view of details of a second design
variant of a drilling/reaming tool, and
[0033] FIG. 5 shows a diagrammatic side view of a further design
variant.
DESCRIPTION OF EXAMPLE EMBODIMENTS
[0034] Directional phrases used herein, such as, for example, left,
right, front, back, top, bottom and derivatives thereof, relate to
the orientation of the elements shown in the drawings and are not
limiting upon the claims unless expressly recited therein.
Identical parts are provided with the same reference number in all
drawings.
[0035] Referring to FIGS. 1-3, a drilling/reaming tool 4, called a
tool for short in the following text, which extends in the
longitudinal direction 2 has a basic body 6 which extends in the
longitudinal direction 2 and in which, in the exemplary embodiment,
two main flutes 8 are made which are wound at a first helix angle
.alpha.1. In the front region, the tool 4 has a reamer head 10. On
its end side, the reamer head 10 is configured as a drill tip 12
which, in the exemplary embodiment, has two major cutting edges 14
(FIGS. 2 and 3) which are connected to one another in the drill
center via a chisel edge 16 (FIG. 2). The respective major cutting
edge 14 is adjoined in the circumferential direction by a clearance
land 18 (FIG. 2) which, in the exemplary embodiment, is configured
in the shape of a cone envelope and extends in each case as far as
the main flute 8 which is assigned to the following major cutting
edge 14. In addition, the fluted region of the basic body 6 is
adjoined by a shank (not shown), by way of which the tool 4 is
clamped into a tool fitting of a metal-cutting machine.
[0036] Referring to FIG. 2, a land 20 is defined between the main
flutes 8, in which land 20 subsequently a plurality of reaming
cutting edges 22 are formed in the region of the reamer head 10 on
the circumferential side in the frontmost region, such that they
adjoin the drill tip 12 directly. As can be seen, in particular,
from FIGS. 1 and 2, the reaming cutting edges 22 are arranged such
that they are recessed somewhat in the longitudinal direction 2
from the clearance land 18 which is in the shape of a cone
envelope. Here, the axial offset x1 between the radially outermost
end of the major cutting edge 14 and the first reaming cutting edge
22 lies in the range of only a few mm, that is to say a fraction
(less than 20%) of a nominal diameter D (FIG. 3) of the tool 4.
[0037] The reaming cutting edges 22 extend in each case
substantially approximately in the radial direction and are
oriented approximately perpendicularly with respect to the
longitudinal direction 2. Here, the reaming cutting edges 22 define
the nominal diameter D of the tool 4. Here, all the reaming cutting
edges 22 lie on the same nominal diameter D. In contrast, the major
cutting edges 14 of the drill tip 12 reach merely as far as a drill
diameter d (FIG. 3) which is slightly smaller than the nominal
diameter D. Here, the nominal diameter D is typically approximately
from 0.2 to 1 mm larger than the drill diameter d.
[0038] Each reaming cutting edge 22 is assigned a reamer flute 24
which is made in the basic body 6 and is configured so as to be
wound at a second helix angle .alpha.2. A respective reaming
cutting edge 22 is adjoined in each case by a reaming minor cutting
edge 26 (FIG. 2) which extends along the respective reamer flute
24. Accordingly, a main minor cutting edge (not shown here in
greater detail) is also provided adjacently to a respective major
cutting edge 14.
[0039] As can be seen, in particular, from FIG. 1, the two helix
angles .alpha.1, .alpha.2 are configured to be different, that is
to say the flutes 8, 24 do not run parallel to one another. Here,
it is provided in the exemplary embodiment of FIGS. 1 to 3 that the
first helix angle .alpha.1 of the main flutes 8 is considerably
greater than the second helix angle .alpha.2 of the reamer flutes
24. In the exemplary embodiment, the first helix angle .alpha.1
lies approximately in the region of 30.degree. and the second helix
angle .alpha.2 lies approximately in the region of approximately
10.degree.. In general, the two helix angles differ approximately
by the factor of from 2 to 4.
[0040] In the exemplary embodiment of FIGS. 1 to 3, this measure
achieves a refinement, in which the individual reamer flutes 24
open into the respective main flute 8, that is to say intersect the
latter as it were. On account of the helical shape, this takes
place at different axial lengths. Here, the axial length L of the
reamer head 10 is defined by the frontmost region of the drill tip
12, that is to say the chisel edge 16 in the exemplary embodiment
and in the rearward part by the end of the longest reamer flute 24
when the latter therefore merges into the main flute 8. Here, the
axial length L of the reamer head 10 preferably lies in the range
of from 2 times to 3 times the nominal diameter D.
[0041] In contrast to the single-piece tool 4 according to FIGS. 1
to 3, the second design variant according to FIG. 4 is also
configured, in particular, for modular tools 4, in which the reamer
head 10 can be inserted into the basic body 6, for example, as an
exchangeable wear part. As an alternative, the reamer head 10 is
fastened in the basic body 6 irreversibly, for example by brazing.
In this design variant, the reamer flutes 24 all end at an
identical axial length which at the same time defines the axial
length L of the reamer head 10.
[0042] As can be seen from FIG. 4, the reamer head 10 has a greater
diameter than a rearward part of the basic body 6, which rearward
part adjoins the reamer head 10. A recessed shoulder 28 is
therefore formed between the reamer head 10 and said rearward part.
Here, the radial depth t of the shoulder 28 is greater than or
equal to the radial depth of the respective reamer flutes 24. In
particular, the radial depth t lies approximately in the range from
0.3 to 2 mm and is generally a fraction of the nominal diameter
(for example, approximately from 2 to 6% of the nominal diameter
D).
[0043] In the exemplary embodiment of FIG. 4, it is provided in
addition that the second helix angle .alpha.2 is greater than the
first helix angle .alpha.1, and the reamer flutes 24 therefore do
not run toward the main flutes 8 and therefore also do not
intersect the latter.
[0044] A common feature of both design variants is that, during
operation, in which the tool 4 rotates about the longitudinal
direction 2, reaming chips which are produced by the reaming
cutting edges 22 are guided away in the reamer flutes 24 and are
transferred into the main flutes 8. In the exemplary embodiment of
FIGS. 1 to 3, this takes place by the reamer flutes 24 opening
directly into the main flutes 8. In the exemplary embodiment of
FIG. 4, this takes place indirectly via the clearance 30 which is
defined by the shoulder 28 and forms an annular space with respect
to a drilled hole wall during operation. The reaming chips pass
into said annular space at the end of the reamer head 10 when they
exit out of the reamer flute 24. As a result of the further
rotation of the tool 4, they subsequently pass into the respective
main flute, that is to say they are taken along by the latter for
further chip discharge.
[0045] The special advantage of the refinement which is described
here is to be seen in the fact that the reaming chips which are
considerably smaller than the main chips which are produced by the
(drilling) major cutting edges 14 are guided in the reamer flutes
24 only over a very short axial length and are subsequently guided
away further together with the main chips in the considerably
larger main flutes 8. This achieves effective transporting away of
chips. In particular, in the case of great axial lengths of the
tool, for example in the case of tools with an axial length which
is greater than from 4 times to 5 times the nominal diameter D, the
risk of chips backing up in the reamer flutes 24 is avoided. In
particular the risk is also avoided that the reaming chips become
jammed between the reaming minor cutting edges 22 and the hole wall
and therefore damage the machined hole wall.
[0046] In particular, long tools 4 of this type often tend to what
is known as rattling, that is to say the tool oscillates in an
undesired manner during operation, which leads to undesired chatter
marks in the hole wall.
[0047] In order to keep this inclination to rattle as low as
possible, an unequal pitch of the reaming cutting edges 22 is
provided. To this end, in the example embodiment, the number of
reaming cutting edges is different on the two lands 20, which is
assisted by different lengths (in the circumferential direction) of
the lands 20. The angular spacing between reaming cutting edges 22
which follow one another is preferably different from one another,
and reaming cutting edges 22 which are assigned to one another,
that is to say, for example, the respectively first reaming cutting
edges 22 which follow the respective major cutting edge 14, are not
arranged so as to lie exactly opposite one another (at an angle of
180.degree.). In addition, furthermore, an unequal pitch of the
major cutting edges 14 is also provided in the exemplary
embodiment, that is to say said major cutting edges 14 are also
arranged with respect to one another at a rotary angle which is not
equal to 180.degree..
[0048] In the exemplary embodiment of FIG. 3, the lands extend over
an angular portion .delta., starting from the respective major
cutting edge 14 as far as to the beginning of the flute. In the
exemplary embodiment, the angle .delta. for the larger land 20 lies
at approximately 115.degree. and that for the shorter land lies at
approximately 85.degree.. Four reaming cutting edges 22 are
provided on the longer land and three reaming cutting edges 22 are
provided on the shorter land.
[0049] In order to achieve uniform loading of the reaming cutting
edges 22, it is provided, furthermore, that the first reaming
cutting edge 22 which follows the respective major cutting edge 14
is arranged offset in a rearward manner by an axial offset x2 (FIG.
1) with regard to the second reaming cutting edge 22. Here, this
offset x2 in relation to the axial height of the following reaming
cutting edge 22 lies approximately in the range from 0.005 to 2 mm.
In FIG. 1, this shoulder is only indicated and is not true to
scale. As a result, the cutting performance to be carried out
during correct operation by the first reaming cutting edge 22 is
reduced and is adapted to the cutting performance of the following
reaming cutting edge 22. On account of the main flute 8 which leads
the first reaming cutting edge 22, the reaming cutting edge 22
would otherwise have to carry out a considerably greater cutting
performance for a defined feed. Here, the axial offset x2 is
selected, in particular, in such a way that, in the case of a
correct feed, for which the tool 4 is designed, the cutting
performances of the reaming cutting edges 22 are largely identical.
The following reaming cutting edges 22 are preferably situated at
an identical axial height.
[0050] Furthermore, a cooling means is provided in the exemplary
embodiment for a high cutting performance. To this end, cooling
channels which run in the solid material of the respective land 20
are machined in the basic body 6. The cooling channels exit at
end-side first openings 32 on the end side of the drill tip 12.
From the cooling channels, in the region of the reamer head 10,
branch channels or bores (not shown in greater detail) lead into
the respective reamer flutes 24 and exit there at second openings
34 in the flute bottom of the respective reamer flute 24 (see FIG.
2).
[0051] FIG. 5 diagrammatically shows a further design variant, in
which the main flute 8 and the reamer flutes 24 are oriented in
opposite directions to one another, that is to say the main flute 8
is oriented at a positive first helix angle .alpha.1 and the reamer
flutes 24 are oriented at a negative second helix angle .alpha.2. A
design variant of this type is used for workpieces with, for
example, precast through holes. During operation, the reaming chips
are conveyed forward toward the drill tip, whereas the drilling
chips are guided away to the rear in the main flute 8.
[0052] While specific example embodiments of the invention have
been described in detail, it will be appreciated by those skilled
in the art that various modifications and alternatives to the
details provided herein could be developed in light of the overall
teachings of the disclosure. Accordingly, the particular
arrangements disclosed are meant to be illustrative only and not
limiting as to the scope of the invention which is to be given the
full breadth of the claims appended and any and all equivalents
thereof.
* * * * *